Second-formant transitions, to a large extent, account for listeners' ability to discriminate place of articulation of speech sounds. Transition contributions are, however, conditioned upon contextual acoustic factors. These include presence of steady states, prior or successive transitions, and first-formant energy. Acoustic environment can contribute to signal discriminability by the redundancy provided through complementary cues or can reduce it by masking. Linguistic factors may influence discriminability by giving different weights to transition values with or without phonetic relevance. Discrimination depends also upon how listeners employ linguistic analysis to assign phonemic labels. Thus, the perception of speech events in different circumstances may involve different interactions of acoustic and linguistic factors. This observation is particularly relevant in the case of hearing impairment, where differences in pathology, age of onset, and type of loss could alter transition processing in different ways (e.g., by increases in frequency difference limens in the second-formant region or by altering experience-based sensitivity to linguistically relevant acoustic distinctions). The proposed studies will examine the perception of signals analogous to second-formant tansitions (hereafter referred to as "second-formant transitions" for brevity) in a series of acoustic contexts selected to be similar to those occurring in natural speech. Results for different sets of signals will be compared in an effort to assess the relative contributions of the several acoustic factors and their interaction with phonetic processing. The results for normal and hearing-impaired listeners will be contrasted in an effort to determine how acoustic-linguistic relationships differ in hearing-impaired individuals with sloping high-frequency hearing loss and impaired speech perception.